The objective of the proposed research is to identify the viral genes involved in herpes simplex virus (HSV)-induced transformation and to elucidate their role in the transformation process. For this purpose, the HSV genome will be cleaved using restriction endonucleases and transformation will be attempted with specific HSV DNA fragments. This method has been used to demonstrate both biochemical and morphologic transformation by individual viral DNA fragments. The identity of essential viral replicative genes encoded by known and newly identified transforming fragments will be determined using ts mutants in marker rescue experiments. Additional genes encoded by fragments will be identified by mutagenesis of the fragment itself and by rescuing induced mutations through coinfection with wild-type virus DNA. Both temperature-sensitive (ts) and specialized mutants, defective in the expression of individual viral antigens, will be isolated. Whether each gene encoded by the transforming fragment is essential for transformation will be determined by attempting to induce transformation using HSV DNA fragments bearing ts or specialized mutations. The functions of essential transforming genes will be elucidated by phenotypic characterization of a) the ts and specialized mutants whose functions are essential for transformation and b) the cells transformed by fragments bearing these mutants. The ability of viral gene products not essential for transformation but expressed in HSV-transformed cells, to alter the phenotype of HSV-transformed cells, will also be examined.